Identification of specific phonon contributions in BCS-type superconductivity of boride-carbide crystals with a layer-like structure

We report On an ab initio study of the BCS-type superconductivity in the intermetallic borocarbides YPd2B2C, YPt2B2C and LaPt2B2C with a layer-like structure. The largest contribution to the electron-phonon coupling constant lambda is identified to come from transverse acoustic phonons at a zone-edge, arking from the atomic vibrations in the boron-transition metal layer. A detailed examination of the atomic geometry in the boron-transition metal layer, the electron-phonon coupling constant lambda, and the logarithmically averaged phonon frequency omega(In), helps explain the relatively higher superconducting temperature T-c of YPd2B2C (20.6 K) compared to that of YPt2B2C (11.3 K) and LaPt2B2C (10.40 K). (C) 2015 Elsevier Ltd. All rights reserved.